The objective for this research is to develop a new form of microscopy, Surface Plasmon Enhanced Microscopy (SPEM). SPEM achieves resolution of 35 nm and is intended to be used for localization of multiple proteins in cells and determine molecular signatures of patients? tumors. The SPEM system generates a database of protein locations within a cell referenced to the position of cellular features (e.g., cell and nuclear membranes, organelles). SPEM can be used to identify molecular signatures of cancer based on protein expression levels and locations. Over time it is expected that a database of SPEM images will be assembled that will serve as a reference for the diagnosis of cancer at the molecular level. SPEM has been designed to seamlessly integrate into the clinical pathology laboratory. The steps required to implement a SPEM analysis are: (1) stain the slide (2) the pathologist reads the slide and marks cells for which a molecular analysis (using a digital coordinate system that is incorporated into the SPEM microscope) is desired (3) SPEM automatically generates the localization and expression level data for the marked cells, and (4) the pathologist analyzes the results in conjunction with the existing immunohistochemical and morphological data to determine the patients? prognoses and select the appropriate therapy. In the R21 research the optical performance of the system will be characterized and the applicability to paraffin-embedded tissue specimens will be demonstrated. In the R33 research the full microscope will be develop and used to generate protein localization and expression data for multiple proteins in a tissue sample.